A blowout preventer (BOP) is generally used to control sub surface pressures that may adversely affect equipment used in drilling oil and gas wells. Fluid pressure in a wellbore can rise suddenly. A sudden rise in pressure can be controlled by adding dense drilling mud into the well; however, this takes time. When a sudden rise in pressure is observed, a blowout preventer is activated to prevent fluid from the well escaping uncontrollably. Blowout preventers are usually situated at the wellhead and can be connected at the top of a riser, at rig level, in coiled tubing injector modules, and blowout preventers arranged in certain top drive systems. The wellhead is connected to casing lining the oil or gas well or to a template at the earth's surface. A concentric pipe, such as drill pipe, production tubular, coiled tubing or tool string can run through the blowout preventer and casing.
A commonly used blowout preventer has a main body having a through bore. The main body is connected inline at the wellhead and the through bore forms part of the main flow channel for the fluids passing through the casing and thus has the same or similar internal diameter as that of the casing. The main body is provided with a pair of opposing ram actuators arranged perpendicular to the flow of fluid through the through bore. The ram actuators are provided with a ram block on the end of each ram actuator for carrying out specific purposes. There are many types of blowout preventers for carrying out these specific purposes, which can include, but are not limited to: pipe ram type, blind ram type, shear ram type and multi-ram type.
Due to numerous faults of blowout preventers, especially in the Gulf of Mexico, new federal guidelines have been established regarding the specifications of blowout preventers. In order to refit blowout preventers that may not meet these new federal guidelines, the well has to be shut down and the blowout preventers brought to the surface in order to retrofit or re-mill these blowout preventers.
A need exists for an assembly that can retrofit or re-mill blowout preventers while minimizing the amount of time the well needs to be shut down.
The present embodiments meet these needs.
The present embodiments are detailed below with reference to the listed Figures.